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From: rosentha@sierra.STANFORD.EDU (rosentha)
Newsgroups: sci.bio,sci.aquaria,sci.environment
Subject: Re: coral reefs, C02, food, and farming.
Message-ID: <18@sierra.STANFORD.EDU>
Date: 3 Dec 90 21:44:35 GMT
References: <720@sierra.stanford.edu> <90337.112001JAHAYES@MIAMIU.BITNET>
Organization: Stanford University
Lines: 23

J Hayes had a point that calcium might be the limiting factor in
C02 fixation, and that C02 is released when Calcium carbonate is
precipitated.  This is true but a little misleading.  Calcium 
Bicarbonate has two bicarbonate ions.  When a reaction removes
a C02 from the disolved HC03- then usually a molecule of CaC03
precipitates out.  This is probably the reaction that coral
uses to build its skeleton.  I would like to know how much
of the corals photosynthesis goes into reef building and how
much goes into respiration.  This reef building activity
seems quite similar to what the freshwater gardeners
call biogenic decalcification, where plants absorb bicarbonates
from the water rather than dissolved C02, and precipitate calcium
carbonate all over the place.  This is not usually a good situatin
in a plant tank, and indicates too much light for the available C02.

	How slowly do reefs really grow?  If a one square kilometer
area grew a 1 cm layer of Calcium carbonate per year, then we would
be fixing 10^10 cc's of carbonate each year.  This probably weighs
on the order of 10^7 kilograms or 20 million pounds.  This is not
that small a number is it?  


		PEter Rosenthal


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